Many of present hybrid cars have structures in which an inverter has a large box-like casing fixed to a chassis, and a motor casing (trans-axle) is arranged under the casing. Consideration may be given to the drive device of the hybrid vehicle that can be mounted in as many as types of hybrid vehicles. In this case, if the device employs two casings, an arrangement of such casings must be optimized for each of the vehicle types. Therefore, it is difficult to standardize parts.
In principle, it is desired that units combined with each other for the operation are integrated and accommodated in one casing. Japanese Patent Laying-Open Nos. 2004-343845, 2001-119961 and 2003-199293 have disclosed drive devices of hybrid vehicles each having a motor and an inverter integrated together.
However, in the drive devices of the hybrid vehicles disclosed in Japanese Patent Laying-Open Nos. 2004-343845 and 2001-119961, the inverter is merely arranged on the motor, and this structure is susceptible to improvement in connection with a vertical position of the center of mass of the vehicle equipped with the device. Further, consideration is not sufficiently given to reduction of a space required for mounting the drive device on the hybrid vehicle.
For allowing the mounting on many types of vehicles, it is desired that the inverter and the motor are arranged within substantially the same contours as an automatic transmission neighboring to an engine in an ordinary vehicle.
In Japanese Patent Laying-Open No. 2003-199293, a water-cooling system is employed as a cooling system of an inverter unit, and an oil-cooling system is employed as a cooling system of a motor unit so that the structure is complicated.